This is a really well article outlining how the man-on-the-side attack on Baidu is carried out. The only flaw here is the logical leap that goes from "Baidu is being hijacked" to "Baidu is being hijacked by the Chinese government"
Whoever is the attacker appears to control the great firewall of China. Who else would that be but the Chinese government?
http://en.wikipedia.org/wiki/Honker_Union#Relationship_with_...
The current DDoS attack just strikes me as too crude a method when they have so many other options available.
If you were going to argue that it's just a retaliation towards GitHub for hosting these projects, then once again there are others sites the government is far more concerned about and they could use DDoS to bring them down with far less publicity than what the GitHub DDoS is generating.
It just doesn't seem to make sense from either the method being used or the motivation behind the attacks.